This invention relates to the field of process chamber pressure control. More particularly the invention relates to systems for and methods of carrying out processes which involve gases in a chamber in which pressure control is needed.
Pressure control for process chambers in various fields are known. For example, in the field of ion implantation devices with a closed-loop process chamber, pressure control systems are known such as the ones disclosed in U.S. Pat. No. 5,672,882 to Day, et al., assigned to Advanced Micro Devices, Inc. in which fluctuations in the pressure within the process chamber are reduced by additions of appropriate amounts of inert gas when the pressure sensed by the vacuum measurement unit drops below a predetermined pressure threshold value. In these prior systems a flow control valve which may be variably opened or closed in response to an electrical control signal, and which can deliver a variable amount of flow gas, is used. In U.S. Pat. No. 6,152,070 to Fairbairn, et al., assigned to Applied Materials, Inc., relating to the field of chemical vapor deposition (“CVD”), a tandem process chamber is disclosed wherein pressure within a processing chamber is controlled by a slit valve as disclosed by Tepman et al. in U.S. Pat. No. 5,226,632 and by Lorimer in U.S. Pat. No. 5,363,872.
In any process chamber of the type which includes a source of gas or vapor at a higher pressure than the exhaust or outlet pressure, which includes chambers which process at positive pressure or at a negative pressure, a valve is needed to maintain pressure close to or at a selected pressure. Prior systems use a variety of valves for this purpose, among which are the aforementioned slit valves and flow control valves, and butterfly valves, proportionally closing valves, needle valves, and the like. The prior valves are relatively expensive, are bulky, and have a large footprint which makes them unsuitable in certain applications. It is an object of the present invention to provide an improved pressure control system for process chambers which include a continuous gas inflow into the chamber and a continuous gas outflow from the chamber. It is also an object to provide an improved method of controlling pressure in a process chamber which includes continuously feeding gas through an inlet to the chamber and continuously removing gas from the chamber, which is free of the disadvantages of prior systems.